sand point surging

I drove a sand point last week for the guy down the street, he is running a hose and a couple of average sprinklers. the pump has started to surge. We put 20 feet of one and onequarter inch pipe in the ground plus the three foot sandpoint.
There is about 6ft of water standing in the pipe what do I look for to fix this problem. There is a red lion 2 horsepower pump running the system, will take all the advice I can get thanks